1 //===- DriverUtils.cpp ----------------------------------------------------===//
2 //
3 //                             The LLVM Linker
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains utility functions for the driver. Because there
11 // are so many small functions, we created this separate file to make
12 // Driver.cpp less cluttered.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "Config.h"
17 #include "Driver.h"
18 #include "Error.h"
19 #include "Memory.h"
20 #include "Symbols.h"
21 #include "llvm/ADT/Optional.h"
22 #include "llvm/ADT/StringSwitch.h"
23 #include "llvm/BinaryFormat/COFF.h"
24 #include "llvm/Object/COFF.h"
25 #include "llvm/Object/WindowsResource.h"
26 #include "llvm/Option/Arg.h"
27 #include "llvm/Option/ArgList.h"
28 #include "llvm/Option/Option.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/FileUtilities.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/Support/Process.h"
33 #include "llvm/Support/Program.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include <memory>
36 
37 using namespace llvm::COFF;
38 using namespace llvm;
39 using llvm::cl::ExpandResponseFiles;
40 using llvm::cl::TokenizeWindowsCommandLine;
41 using llvm::sys::Process;
42 
43 namespace lld {
44 namespace coff {
45 namespace {
46 
47 const uint16_t SUBLANG_ENGLISH_US = 0x0409;
48 const uint16_t RT_MANIFEST = 24;
49 
50 class Executor {
51 public:
52   explicit Executor(StringRef S) : Prog(Saver.save(S)) {}
53   void add(StringRef S) { Args.push_back(Saver.save(S)); }
54   void add(std::string &S) { Args.push_back(Saver.save(S)); }
55   void add(Twine S) { Args.push_back(Saver.save(S)); }
56   void add(const char *S) { Args.push_back(Saver.save(S)); }
57 
58   void run() {
59     ErrorOr<std::string> ExeOrErr = sys::findProgramByName(Prog);
60     if (auto EC = ExeOrErr.getError())
61       fatal(EC, "unable to find " + Prog + " in PATH: ");
62     StringRef Exe = Saver.save(*ExeOrErr);
63     Args.insert(Args.begin(), Exe);
64 
65     std::vector<const char *> Vec;
66     for (StringRef S : Args)
67       Vec.push_back(S.data());
68     Vec.push_back(nullptr);
69 
70     if (sys::ExecuteAndWait(Args[0], Vec.data()) != 0)
71       fatal("ExecuteAndWait failed: " +
72             llvm::join(Args.begin(), Args.end(), " "));
73   }
74 
75 private:
76   StringRef Prog;
77   std::vector<StringRef> Args;
78 };
79 
80 } // anonymous namespace
81 
82 // Returns /machine's value.
83 MachineTypes getMachineType(StringRef S) {
84   MachineTypes MT = StringSwitch<MachineTypes>(S.lower())
85                         .Cases("x64", "amd64", AMD64)
86                         .Cases("x86", "i386", I386)
87                         .Case("arm", ARMNT)
88                         .Default(IMAGE_FILE_MACHINE_UNKNOWN);
89   if (MT != IMAGE_FILE_MACHINE_UNKNOWN)
90     return MT;
91   fatal("unknown /machine argument: " + S);
92 }
93 
94 StringRef machineToStr(MachineTypes MT) {
95   switch (MT) {
96   case ARMNT:
97     return "arm";
98   case AMD64:
99     return "x64";
100   case I386:
101     return "x86";
102   default:
103     llvm_unreachable("unknown machine type");
104   }
105 }
106 
107 // Parses a string in the form of "<integer>[,<integer>]".
108 void parseNumbers(StringRef Arg, uint64_t *Addr, uint64_t *Size) {
109   StringRef S1, S2;
110   std::tie(S1, S2) = Arg.split(',');
111   if (S1.getAsInteger(0, *Addr))
112     fatal("invalid number: " + S1);
113   if (Size && !S2.empty() && S2.getAsInteger(0, *Size))
114     fatal("invalid number: " + S2);
115 }
116 
117 // Parses a string in the form of "<integer>[.<integer>]".
118 // If second number is not present, Minor is set to 0.
119 void parseVersion(StringRef Arg, uint32_t *Major, uint32_t *Minor) {
120   StringRef S1, S2;
121   std::tie(S1, S2) = Arg.split('.');
122   if (S1.getAsInteger(0, *Major))
123     fatal("invalid number: " + S1);
124   *Minor = 0;
125   if (!S2.empty() && S2.getAsInteger(0, *Minor))
126     fatal("invalid number: " + S2);
127 }
128 
129 // Parses a string in the form of "<subsystem>[,<integer>[.<integer>]]".
130 void parseSubsystem(StringRef Arg, WindowsSubsystem *Sys, uint32_t *Major,
131                     uint32_t *Minor) {
132   StringRef SysStr, Ver;
133   std::tie(SysStr, Ver) = Arg.split(',');
134   *Sys = StringSwitch<WindowsSubsystem>(SysStr.lower())
135     .Case("boot_application", IMAGE_SUBSYSTEM_WINDOWS_BOOT_APPLICATION)
136     .Case("console", IMAGE_SUBSYSTEM_WINDOWS_CUI)
137     .Case("efi_application", IMAGE_SUBSYSTEM_EFI_APPLICATION)
138     .Case("efi_boot_service_driver", IMAGE_SUBSYSTEM_EFI_BOOT_SERVICE_DRIVER)
139     .Case("efi_rom", IMAGE_SUBSYSTEM_EFI_ROM)
140     .Case("efi_runtime_driver", IMAGE_SUBSYSTEM_EFI_RUNTIME_DRIVER)
141     .Case("native", IMAGE_SUBSYSTEM_NATIVE)
142     .Case("posix", IMAGE_SUBSYSTEM_POSIX_CUI)
143     .Case("windows", IMAGE_SUBSYSTEM_WINDOWS_GUI)
144     .Default(IMAGE_SUBSYSTEM_UNKNOWN);
145   if (*Sys == IMAGE_SUBSYSTEM_UNKNOWN)
146     fatal("unknown subsystem: " + SysStr);
147   if (!Ver.empty())
148     parseVersion(Ver, Major, Minor);
149 }
150 
151 // Parse a string of the form of "<from>=<to>".
152 // Results are directly written to Config.
153 void parseAlternateName(StringRef S) {
154   StringRef From, To;
155   std::tie(From, To) = S.split('=');
156   if (From.empty() || To.empty())
157     fatal("/alternatename: invalid argument: " + S);
158   auto It = Config->AlternateNames.find(From);
159   if (It != Config->AlternateNames.end() && It->second != To)
160     fatal("/alternatename: conflicts: " + S);
161   Config->AlternateNames.insert(It, std::make_pair(From, To));
162 }
163 
164 // Parse a string of the form of "<from>=<to>".
165 // Results are directly written to Config.
166 void parseMerge(StringRef S) {
167   StringRef From, To;
168   std::tie(From, To) = S.split('=');
169   if (From.empty() || To.empty())
170     fatal("/merge: invalid argument: " + S);
171   auto Pair = Config->Merge.insert(std::make_pair(From, To));
172   bool Inserted = Pair.second;
173   if (!Inserted) {
174     StringRef Existing = Pair.first->second;
175     if (Existing != To)
176       warn(S + ": already merged into " + Existing);
177   }
178 }
179 
180 static uint32_t parseSectionAttributes(StringRef S) {
181   uint32_t Ret = 0;
182   for (char C : S.lower()) {
183     switch (C) {
184     case 'd':
185       Ret |= IMAGE_SCN_MEM_DISCARDABLE;
186       break;
187     case 'e':
188       Ret |= IMAGE_SCN_MEM_EXECUTE;
189       break;
190     case 'k':
191       Ret |= IMAGE_SCN_MEM_NOT_CACHED;
192       break;
193     case 'p':
194       Ret |= IMAGE_SCN_MEM_NOT_PAGED;
195       break;
196     case 'r':
197       Ret |= IMAGE_SCN_MEM_READ;
198       break;
199     case 's':
200       Ret |= IMAGE_SCN_MEM_SHARED;
201       break;
202     case 'w':
203       Ret |= IMAGE_SCN_MEM_WRITE;
204       break;
205     default:
206       fatal("/section: invalid argument: " + S);
207     }
208   }
209   return Ret;
210 }
211 
212 // Parses /section option argument.
213 void parseSection(StringRef S) {
214   StringRef Name, Attrs;
215   std::tie(Name, Attrs) = S.split(',');
216   if (Name.empty() || Attrs.empty())
217     fatal("/section: invalid argument: " + S);
218   Config->Section[Name] = parseSectionAttributes(Attrs);
219 }
220 
221 // Parses a string in the form of "EMBED[,=<integer>]|NO".
222 // Results are directly written to Config.
223 void parseManifest(StringRef Arg) {
224   if (Arg.equals_lower("no")) {
225     Config->Manifest = Configuration::No;
226     return;
227   }
228   if (!Arg.startswith_lower("embed"))
229     fatal("invalid option " + Arg);
230   Config->Manifest = Configuration::Embed;
231   Arg = Arg.substr(strlen("embed"));
232   if (Arg.empty())
233     return;
234   if (!Arg.startswith_lower(",id="))
235     fatal("invalid option " + Arg);
236   Arg = Arg.substr(strlen(",id="));
237   if (Arg.getAsInteger(0, Config->ManifestID))
238     fatal("invalid option " + Arg);
239 }
240 
241 // Parses a string in the form of "level=<string>|uiAccess=<string>|NO".
242 // Results are directly written to Config.
243 void parseManifestUAC(StringRef Arg) {
244   if (Arg.equals_lower("no")) {
245     Config->ManifestUAC = false;
246     return;
247   }
248   for (;;) {
249     Arg = Arg.ltrim();
250     if (Arg.empty())
251       return;
252     if (Arg.startswith_lower("level=")) {
253       Arg = Arg.substr(strlen("level="));
254       std::tie(Config->ManifestLevel, Arg) = Arg.split(" ");
255       continue;
256     }
257     if (Arg.startswith_lower("uiaccess=")) {
258       Arg = Arg.substr(strlen("uiaccess="));
259       std::tie(Config->ManifestUIAccess, Arg) = Arg.split(" ");
260       continue;
261     }
262     fatal("invalid option " + Arg);
263   }
264 }
265 
266 // An RAII temporary file class that automatically removes a temporary file.
267 namespace {
268 class TemporaryFile {
269 public:
270   TemporaryFile(StringRef Prefix, StringRef Extn, StringRef Contents = "") {
271     SmallString<128> S;
272     if (auto EC = sys::fs::createTemporaryFile("lld-" + Prefix, Extn, S))
273       fatal(EC, "cannot create a temporary file");
274     Path = S.str();
275 
276     if (!Contents.empty()) {
277       std::error_code EC;
278       raw_fd_ostream OS(Path, EC, sys::fs::F_None);
279       if (EC)
280         fatal(EC, "failed to open " + Path);
281       OS << Contents;
282     }
283   }
284 
285   TemporaryFile(TemporaryFile &&Obj) {
286     std::swap(Path, Obj.Path);
287   }
288 
289   ~TemporaryFile() {
290     if (Path.empty())
291       return;
292     if (sys::fs::remove(Path))
293       fatal("failed to remove " + Path);
294   }
295 
296   // Returns a memory buffer of this temporary file.
297   // Note that this function does not leave the file open,
298   // so it is safe to remove the file immediately after this function
299   // is called (you cannot remove an opened file on Windows.)
300   std::unique_ptr<MemoryBuffer> getMemoryBuffer() {
301     // IsVolatileSize=true forces MemoryBuffer to not use mmap().
302     return check(MemoryBuffer::getFile(Path, /*FileSize=*/-1,
303                                        /*RequiresNullTerminator=*/false,
304                                        /*IsVolatileSize=*/true),
305                  "could not open " + Path);
306   }
307 
308   std::string Path;
309 };
310 }
311 
312 // Create the default manifest file as a temporary file.
313 TemporaryFile createDefaultXml() {
314   // Create a temporary file.
315   TemporaryFile File("defaultxml", "manifest");
316 
317   // Open the temporary file for writing.
318   std::error_code EC;
319   raw_fd_ostream OS(File.Path, EC, sys::fs::F_Text);
320   if (EC)
321     fatal(EC, "failed to open " + File.Path);
322 
323   // Emit the XML. Note that we do *not* verify that the XML attributes are
324   // syntactically correct. This is intentional for link.exe compatibility.
325   OS << "<?xml version=\"1.0\" standalone=\"yes\"?>\n"
326      << "<assembly xmlns=\"urn:schemas-microsoft-com:asm.v1\"\n"
327      << "          manifestVersion=\"1.0\">\n";
328   if (Config->ManifestUAC) {
329     OS << "  <trustInfo>\n"
330        << "    <security>\n"
331        << "      <requestedPrivileges>\n"
332        << "         <requestedExecutionLevel level=" << Config->ManifestLevel
333        << " uiAccess=" << Config->ManifestUIAccess << "/>\n"
334        << "      </requestedPrivileges>\n"
335        << "    </security>\n"
336        << "  </trustInfo>\n";
337     if (!Config->ManifestDependency.empty()) {
338       OS << "  <dependency>\n"
339          << "    <dependentAssembly>\n"
340          << "      <assemblyIdentity " << Config->ManifestDependency << " />\n"
341          << "    </dependentAssembly>\n"
342          << "  </dependency>\n";
343     }
344   }
345   OS << "</assembly>\n";
346   OS.close();
347   return File;
348 }
349 
350 static std::string readFile(StringRef Path) {
351   std::unique_ptr<MemoryBuffer> MB =
352       check(MemoryBuffer::getFile(Path), "could not open " + Path);
353   return MB->getBuffer();
354 }
355 
356 static std::string createManifestXml() {
357   // Create the default manifest file.
358   TemporaryFile File1 = createDefaultXml();
359   if (Config->ManifestInput.empty())
360     return readFile(File1.Path);
361 
362   // If manifest files are supplied by the user using /MANIFESTINPUT
363   // option, we need to merge them with the default manifest.
364   TemporaryFile File2("user", "manifest");
365 
366   Executor E("mt.exe");
367   E.add("/manifest");
368   E.add(File1.Path);
369   for (StringRef Filename : Config->ManifestInput) {
370     E.add("/manifest");
371     E.add(Filename);
372   }
373   E.add("/nologo");
374   E.add("/out:" + StringRef(File2.Path));
375   E.run();
376   return readFile(File2.Path);
377 }
378 
379 static std::unique_ptr<MemoryBuffer>
380 createMemoryBufferForManifestRes(size_t ManifestSize) {
381   size_t ResSize = alignTo(object::WIN_RES_MAGIC_SIZE +
382                            object::WIN_RES_NULL_ENTRY_SIZE +
383                            sizeof(object::WinResHeaderPrefix) +
384                            sizeof(object::WinResIDs) +
385                            sizeof(object::WinResHeaderSuffix) +
386                            ManifestSize,
387                            object::WIN_RES_DATA_ALIGNMENT);
388   return MemoryBuffer::getNewMemBuffer(ResSize);
389 }
390 
391 static void writeResFileHeader(char *&Buf) {
392   memcpy(Buf, COFF::WinResMagic, sizeof(COFF::WinResMagic));
393   Buf += sizeof(COFF::WinResMagic);
394   memset(Buf, 0, object::WIN_RES_NULL_ENTRY_SIZE);
395   Buf += object::WIN_RES_NULL_ENTRY_SIZE;
396 }
397 
398 static void writeResEntryHeader(char *&Buf, size_t ManifestSize) {
399   // Write the prefix.
400   auto *Prefix = reinterpret_cast<object::WinResHeaderPrefix *>(Buf);
401   Prefix->DataSize = ManifestSize;
402   Prefix->HeaderSize = sizeof(object::WinResHeaderPrefix) +
403                        sizeof(object::WinResIDs) +
404                        sizeof(object::WinResHeaderSuffix);
405   Buf += sizeof(object::WinResHeaderPrefix);
406 
407   // Write the Type/Name IDs.
408   auto *IDs = reinterpret_cast<object::WinResIDs *>(Buf);
409   IDs->setType(RT_MANIFEST);
410   IDs->setName(Config->ManifestID);
411   Buf += sizeof(object::WinResIDs);
412 
413   // Write the suffix.
414   auto *Suffix = reinterpret_cast<object::WinResHeaderSuffix *>(Buf);
415   Suffix->DataVersion = 0;
416   Suffix->MemoryFlags = object::WIN_RES_PURE_MOVEABLE;
417   Suffix->Language = SUBLANG_ENGLISH_US;
418   Suffix->Version = 0;
419   Suffix->Characteristics = 0;
420   Buf += sizeof(object::WinResHeaderSuffix);
421 }
422 
423 // Create a resource file containing a manifest XML.
424 std::unique_ptr<MemoryBuffer> createManifestRes() {
425   std::string Manifest = createManifestXml();
426 
427   std::unique_ptr<MemoryBuffer> Res =
428       createMemoryBufferForManifestRes(Manifest.size());
429 
430   char *Buf = const_cast<char *>(Res->getBufferStart());
431   writeResFileHeader(Buf);
432   writeResEntryHeader(Buf, Manifest.size());
433 
434   // Copy the manifest data into the .res file.
435   std::copy(Manifest.begin(), Manifest.end(), Buf);
436   return std::move(Res);
437 }
438 
439 void createSideBySideManifest() {
440   std::string Path = Config->ManifestFile;
441   if (Path == "")
442     Path = Config->OutputFile + ".manifest";
443   std::error_code EC;
444   raw_fd_ostream Out(Path, EC, sys::fs::F_Text);
445   if (EC)
446     fatal(EC, "failed to create manifest");
447   Out << createManifestXml();
448 }
449 
450 // Parse a string in the form of
451 // "<name>[=<internalname>][,@ordinal[,NONAME]][,DATA][,PRIVATE]"
452 // or "<name>=<dllname>.<name>".
453 // Used for parsing /export arguments.
454 Export parseExport(StringRef Arg) {
455   Export E;
456   StringRef Rest;
457   std::tie(E.Name, Rest) = Arg.split(",");
458   if (E.Name.empty())
459     goto err;
460 
461   if (E.Name.find('=') != StringRef::npos) {
462     StringRef X, Y;
463     std::tie(X, Y) = E.Name.split("=");
464 
465     // If "<name>=<dllname>.<name>".
466     if (Y.find(".") != StringRef::npos) {
467       E.Name = X;
468       E.ForwardTo = Y;
469       return E;
470     }
471 
472     E.ExtName = X;
473     E.Name = Y;
474     if (E.Name.empty())
475       goto err;
476   }
477 
478   // If "<name>=<internalname>[,@ordinal[,NONAME]][,DATA][,PRIVATE]"
479   while (!Rest.empty()) {
480     StringRef Tok;
481     std::tie(Tok, Rest) = Rest.split(",");
482     if (Tok.equals_lower("noname")) {
483       if (E.Ordinal == 0)
484         goto err;
485       E.Noname = true;
486       continue;
487     }
488     if (Tok.equals_lower("data")) {
489       E.Data = true;
490       continue;
491     }
492     if (Tok.equals_lower("constant")) {
493       E.Constant = true;
494       continue;
495     }
496     if (Tok.equals_lower("private")) {
497       E.Private = true;
498       continue;
499     }
500     if (Tok.startswith("@")) {
501       int32_t Ord;
502       if (Tok.substr(1).getAsInteger(0, Ord))
503         goto err;
504       if (Ord <= 0 || 65535 < Ord)
505         goto err;
506       E.Ordinal = Ord;
507       continue;
508     }
509     goto err;
510   }
511   return E;
512 
513 err:
514   fatal("invalid /export: " + Arg);
515 }
516 
517 static StringRef undecorate(StringRef Sym) {
518   if (Config->Machine != I386)
519     return Sym;
520   return Sym.startswith("_") ? Sym.substr(1) : Sym;
521 }
522 
523 // Performs error checking on all /export arguments.
524 // It also sets ordinals.
525 void fixupExports() {
526   // Symbol ordinals must be unique.
527   std::set<uint16_t> Ords;
528   for (Export &E : Config->Exports) {
529     if (E.Ordinal == 0)
530       continue;
531     if (!Ords.insert(E.Ordinal).second)
532       fatal("duplicate export ordinal: " + E.Name);
533   }
534 
535   for (Export &E : Config->Exports) {
536     SymbolBody *Sym = E.Sym;
537     if (!E.ForwardTo.empty() || !Sym) {
538       E.SymbolName = E.Name;
539     } else {
540       if (auto *U = dyn_cast<Undefined>(Sym))
541         if (U->WeakAlias)
542           Sym = U->WeakAlias;
543       E.SymbolName = Sym->getName();
544     }
545   }
546 
547   for (Export &E : Config->Exports) {
548     if (!E.ForwardTo.empty()) {
549       E.ExportName = undecorate(E.Name);
550     } else {
551       E.ExportName = undecorate(E.ExtName.empty() ? E.Name : E.ExtName);
552     }
553   }
554 
555   // Uniquefy by name.
556   std::map<StringRef, Export *> Map;
557   std::vector<Export> V;
558   for (Export &E : Config->Exports) {
559     auto Pair = Map.insert(std::make_pair(E.ExportName, &E));
560     bool Inserted = Pair.second;
561     if (Inserted) {
562       V.push_back(E);
563       continue;
564     }
565     Export *Existing = Pair.first->second;
566     if (E == *Existing || E.Name != Existing->Name)
567       continue;
568     warn("duplicate /export option: " + E.Name);
569   }
570   Config->Exports = std::move(V);
571 
572   // Sort by name.
573   std::sort(Config->Exports.begin(), Config->Exports.end(),
574             [](const Export &A, const Export &B) {
575               return A.ExportName < B.ExportName;
576             });
577 }
578 
579 void assignExportOrdinals() {
580   // Assign unique ordinals if default (= 0).
581   uint16_t Max = 0;
582   for (Export &E : Config->Exports)
583     Max = std::max(Max, E.Ordinal);
584   for (Export &E : Config->Exports)
585     if (E.Ordinal == 0)
586       E.Ordinal = ++Max;
587 }
588 
589 // Parses a string in the form of "key=value" and check
590 // if value matches previous values for the same key.
591 void checkFailIfMismatch(StringRef Arg) {
592   StringRef K, V;
593   std::tie(K, V) = Arg.split('=');
594   if (K.empty() || V.empty())
595     fatal("/failifmismatch: invalid argument: " + Arg);
596   StringRef Existing = Config->MustMatch[K];
597   if (!Existing.empty() && V != Existing)
598     fatal("/failifmismatch: mismatch detected: " + Existing + " and " + V +
599           " for key " + K);
600   Config->MustMatch[K] = V;
601 }
602 
603 // Convert Windows resource files (.res files) to a .obj file
604 // using cvtres.exe.
605 std::unique_ptr<MemoryBuffer>
606 convertResToCOFF(const std::vector<MemoryBufferRef> &MBs) {
607   object::WindowsResourceParser Parser;
608 
609   for (MemoryBufferRef MB : MBs) {
610     std::unique_ptr<object::Binary> Bin = check(object::createBinary(MB));
611     object::WindowsResource *RF = dyn_cast<object::WindowsResource>(Bin.get());
612     if (!RF)
613       fatal("cannot compile non-resource file as resource");
614     if (auto EC = Parser.parse(RF))
615       fatal(EC, "failed to parse .res file");
616   }
617 
618   Expected<std::unique_ptr<MemoryBuffer>> E =
619       llvm::object::writeWindowsResourceCOFF(Config->Machine, Parser);
620   if (!E)
621     fatal(errorToErrorCode(E.takeError()), "failed to write .res to COFF");
622   return std::move(E.get());
623 }
624 
625 // Run MSVC link.exe for given in-memory object files.
626 // Command line options are copied from those given to LLD.
627 // This is for the /msvclto option.
628 void runMSVCLinker(std::string Rsp, ArrayRef<StringRef> Objects) {
629   // Write the in-memory object files to disk.
630   std::vector<TemporaryFile> Temps;
631   for (StringRef S : Objects) {
632     Temps.emplace_back("lto", "obj", S);
633     Rsp += quote(Temps.back().Path) + "\n";
634   }
635 
636   log("link.exe " + Rsp);
637 
638   // Run MSVC link.exe.
639   Temps.emplace_back("lto", "rsp", Rsp);
640   Executor E("link.exe");
641   E.add(Twine("@" + Temps.back().Path));
642   E.run();
643 }
644 
645 // Create OptTable
646 
647 // Create prefix string literals used in Options.td
648 #define PREFIX(NAME, VALUE) const char *const NAME[] = VALUE;
649 #include "Options.inc"
650 #undef PREFIX
651 
652 // Create table mapping all options defined in Options.td
653 static const llvm::opt::OptTable::Info infoTable[] = {
654 #define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12)      \
655   {X1, X2, X10,         X11,         OPT_##ID, llvm::opt::Option::KIND##Class, \
656    X9, X8, OPT_##GROUP, OPT_##ALIAS, X7,       X12},
657 #include "Options.inc"
658 #undef OPTION
659 };
660 
661 class COFFOptTable : public llvm::opt::OptTable {
662 public:
663   COFFOptTable() : OptTable(infoTable, true) {}
664 };
665 
666 // Parses a given list of options.
667 opt::InputArgList ArgParser::parse(ArrayRef<const char *> ArgsArr) {
668   // First, replace respnose files (@<file>-style options).
669   std::vector<const char *> Argv = replaceResponseFiles(ArgsArr);
670 
671   // Make InputArgList from string vectors.
672   COFFOptTable Table;
673   unsigned MissingIndex;
674   unsigned MissingCount;
675   opt::InputArgList Args = Table.ParseArgs(Argv, MissingIndex, MissingCount);
676 
677   // Print the real command line if response files are expanded.
678   if (Args.hasArg(OPT_verbose) && ArgsArr.size() != Argv.size()) {
679     std::string Msg = "Command line:";
680     for (const char *S : Argv)
681       Msg += " " + std::string(S);
682     message(Msg);
683   }
684 
685   if (MissingCount)
686     fatal(Twine(Args.getArgString(MissingIndex)) + ": missing argument");
687   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
688     warn("ignoring unknown argument: " + Arg->getSpelling());
689   return Args;
690 }
691 
692 // link.exe has an interesting feature. If LINK or _LINK_ environment
693 // variables exist, their contents are handled as command line strings.
694 // So you can pass extra arguments using them.
695 opt::InputArgList ArgParser::parseLINK(std::vector<const char *> Args) {
696   // Concatenate LINK env and command line arguments, and then parse them.
697   if (Optional<std::string> S = Process::GetEnv("LINK")) {
698     std::vector<const char *> V = tokenize(*S);
699     Args.insert(Args.begin(), V.begin(), V.end());
700   }
701   if (Optional<std::string> S = Process::GetEnv("_LINK_")) {
702     std::vector<const char *> V = tokenize(*S);
703     Args.insert(Args.begin(), V.begin(), V.end());
704   }
705   return parse(Args);
706 }
707 
708 std::vector<const char *> ArgParser::tokenize(StringRef S) {
709   SmallVector<const char *, 16> Tokens;
710   cl::TokenizeWindowsCommandLine(S, Saver, Tokens);
711   return std::vector<const char *>(Tokens.begin(), Tokens.end());
712 }
713 
714 // Creates a new command line by replacing options starting with '@'
715 // character. '@<filename>' is replaced by the file's contents.
716 std::vector<const char *>
717 ArgParser::replaceResponseFiles(std::vector<const char *> Argv) {
718   SmallVector<const char *, 256> Tokens(Argv.data(), Argv.data() + Argv.size());
719   ExpandResponseFiles(Saver, TokenizeWindowsCommandLine, Tokens);
720   return std::vector<const char *>(Tokens.begin(), Tokens.end());
721 }
722 
723 void printHelp(const char *Argv0) {
724   COFFOptTable Table;
725   Table.PrintHelp(outs(), Argv0, "LLVM Linker", false);
726 }
727 
728 } // namespace coff
729 } // namespace lld
730